help w/determining coolant leak

[fireguy12117]

i need some help with witch way to go on verifying a coolant leak issue.

so far i have white exhaust and a coolant level that dropped over a period of a couple months light city driving. no matter how long of a trip i take, the exhaust stinks and stays white.

today is when i discovered the low coolant level, so i wasn't sure what to next but tried my best at a compression check. i got 110-130psi on 5 out of 6 cylinders with a POS harbor freight thing. i couldn't get the rear pass side cylinder 'cuz the air box makes it too tight. also, i couldn't tell a difference on any plug to indicate being fouled by coolant. they all looked pretty good and identical.

i was imagining that if i had good compression on the cylinders that maybe it was an intake gasket leaking into the cylinder.

the T-stat operates like it should, opens after some driving. the temp gauge fluctuates some...so...my next step is to try what was suggested in another thread on running the truck and looking for bubbles in the rad fill cap. in my experience i've always had a geyser eruption when i did this, but we'll see.

im in a pinch. i was supposed to take this money pit up north in 3 days, now i dont know what the heck ima do since there is a good change i need 4wd where we are going but cant risk blowing a head gasket in the middle of BFE.

 

[masterbrenden]

by the sounds of it the head gasket or the intake gasket may be bad
what is the info on the truck

 

[fireguy12117]

well, i know i have a problem, i am trying to determine which one it is between a head or intake gasket. since this is somewhat of a time critical issue i'd like to know which one i am dealing with....

anyhow, info is in the signature: 93 4.0 auto 4x4.

i did the engine running rad cap off test just now and i now have more questions than answers.

coolant reservoir was well below cold fill level. rad level was low. topped rad off, started truck and immediately got bubbles. a lot. i have rebuild this motor from the heads up this summer but don't recall burping the coolant system so now, how do you determine air bubbles in the system from air bubbles coming from a pressurized, leaking combustion chamber via the head gasket?

the bubbles tapered off to nearly nothing but an occiasional bubble. also the level fluctuated continuously, dunno if that's normal. it didn't bounce around too much, but at one point it dropped an inch or so down, could have been the t-stat opening? anyhow, does it make a difference one or two bubbles, versus a continuous stream of bubbles if you had a blown head gasket?

and if in fact one does have a leaking/blown head gasket, what other symptoms would accompany that? and lastly, if is a blown head gasket and the pressure inside the combustion chamber is well above that of the coolant system, how the heck do you loose coolant?! if i am pressurizing the coolant, shouldn't there be some in the overflow tank? mine was nearly bone dry.

 

[masterbrenden]

get it all burped out then while running give it a burst to about 3/4 throttle and let it idle down if there is alot of bubbles it is more likely a combustion gas

 

[Big Jim M]

Most times the leak you are looking for is EXTERNAL! You simply ain't found it yet. Forget about the color of the tail pipe. If you have a leak in a head gassket that will allow the coolant into the combustion chamber then the same leak will allow a LOT MORE combustion into the radiator.
Do this.. park with the front end uphill then jack up the drivers side front so the fill cap is the highest part of the cooling system. EVEN higher than the hoses to the heater.. (lots of guys forget about the heater) Now turn the heat to it's highest mark and start the engine. With the cap off pour coolant into the radiator until it is full..This usually takes five minutes or more.. Then put the cap on and fill the coolant tank to the cold level.
Now go for a drive.... If the coolant tank fills up and over flows then you have a headgasket leak.. If not then the leak is elsewhere... USUALLY it is external.. Look closely.
Jim

 

[beaujt]

check your oil too... no one else mentioned it so i figured i would. cuz white smoke sure sounds like a head gasket to me. and if you're oil is gray, like a milky gray(cuz water got in it) then you've definitely got a head gasket, and/or if oil is in your coolant, that could also tell ya.

 

[fireguy12117]

im lost cuz i have clear oil and clear coolant. at least on a first pass look at everything. a friend at work said if he could remember he'd bring in a pressure gauge for the coolant system so i can work with real data.

this truck isn't a daily driver so i don't know how much that plays into things, that it hasn't had too many miles since the head swap. anyhow, im all about searching for an external leak, hell, id be happy to have that problem, but this exhaust just stinks and stays white, so i keep getting tripped up by that.

big Jim- your saying to fill the coolant system to capacity, and look for coolant getting blown/pushed/forced into the overflow tank- indicating a breach between a cylinder and the coolant system? how does the radiator cap seal off the coolant system, but allow overpressure into the tank? is the cap like a pressure relief device of sorts?

 

[Big Jim M]

The cap has a good seal against the radiator, Then it has a 16lb spring that holds the seal tightly against the radiator pressure. When the pressure gets greater than 16lb the spring force is overcome and the extra (now extra) coolant goes into the coolant tank. This is normal every time the engine reaches running temperature. Then when the engine is turned off and the coolant temp goes down the coolant SHRINKS and SUCKS back the coolant that only recently was pushed into the coolant tank..
The reason for this system is RUST.. Having any air in the system allows rust to grow and that ain't good.. So the system is engineered to contain only liquid.
Big JIm

 

[Larry's shee]

X-2 on test procedures here. Son's 4.0 had bad intake gasket, leaking left front by a/c p/s. Also water in oil and steam. Blown bad enough to leak into vally and intake port. Also going to do leak down and compression test. Torking intake wouldn't have worked in this case. Pretty iffy on the BFE Breakdown.

 

[fireguy12117]

Big Jim- thanks, that's exactly what i was imagining was going on, so...with an empty coolant tank i could possibly have let air into the system...it would depend on that spring action...anyhow, i didn't get the tester and this weekend we're gone, have to get back at it monday.

Wife's aware of what it means takin the 2wd, but in her words "you did well in Maine a couple years ago". we were heading to my sisters just before new years and caught a nice little east coast storm that took my drive from 8 to 16 hours, to where it was me and the few plow trucks out. so, we're gonna chance getting stuck in snow versus stuck with a blown motor.

OH! ok, who's got input on felpro lower intake gaskets- that's whats in there...i guess i am trying to convince myself its an intake gasket as opposed to a cracked head...but i recall felpros being frowned upon?

 

[fireguy12117]

i got a hold of a tester and froze my nutz off getting some numbers. good news is, coolant pressures didn't point to anything. the bad news is, the coolant pressures didn't point to anything.

i put the gauge on the rad. cap and started the truck. the pressure according to the gauge settled around 4-6psi. i let it run a bit longer and never saw the needle rise past that- which points to no combustion chamber pressures getting into coolant system. shut the engine off and pumped up the gauge to 14-16psi or so and in 5 minutes time the pressure slowly dropped 5psi or so and seemed to stay until i pulled the whole thing off.

i thought i would see the needle peg if there was a head gasket leak...
also the coolant level did not seem to drop from the last time i originally tried all the stuff in the previous posts, plus having done a bit of driving with the truck in the last couple weeks. so WTF...exhaust still stinks something bad, coolant level stays consistent, and there isn't excessive pressure in the system.

 

[Big Jim M]

I have no idea where all this started. But like most low coolant levels I'd guess you have a small drip somewhere outside the engine.
I'd park her facing uphill and jack up the side with the radiator cap. Then I'd turn the heater on and with the cap off I'd run her 30 miniutes or more all the while filling the radiator to completely FULL then when the whole underhood coolant parts were at the prescribed 200* I'd put the cap (a new one) back on and fill the coolant TANK to the full mark. Then I'd drive her 20 miles and come back and park her in such a place that I could crawl around under her and look for a DRIP of coolant with a flashlight. Upon finding that single drip I'd repair it and be on my way.
Too many guys get all upset at coolant losses and fail to think about the cold weather shrinking hoses and gaskets that have contained the coolant all these years and finally allowed a little coolant to escape.
The check you just did has allowed you to FORGET about the smell in the exhaust.
Big JIm

 

[fireguy12117]

my goal is to try to find out why something isn't combusting correctly. i got in too big of a rush reassembling the motor after finding the wrong heads installed and didn't burp the coolant system properly. forgetting that, seeing a low coolant level and white smoke exhaust led me to establish if there was a head gasket leak. i don't really care about an external leak at this point. the test i just did eliminated a head gasket leak as far as i can tell, but hasn't made me forget the smell- something isn't right about it.

i will perform your procedure as a matter of ensuring the integrity of the coolant system since i didn't do it right a while back, but i just sailed off into mystery territory.

 

[Big Jim M]

Fireguy... Yours is maybe the most common problem with our little engines. Guys don't spend the time finding the exterior leak and automatically assume the head gasket or intake gasket.. About 99% of headgasket leaks and general overheating is caused by a small almost invisable external leak!
These leaks are almost NEVER able to be seen from a casual look from under the hood.. By crawling your butt under the ride with a flashlight you will have a much better chance of finding a leak.
Forget about the exhaust until you know FOR SURE your coolant system is keeping it's coolant inside.
Big JIm

 

[Big Jim M]

I have to admit here that my OWN 31 year old son has just burnt up a headgasket by not completely refilling his coolant system after replaceing his coolant this winter.. Everything was good but he just HAD to mess with his engine.. And there went a head gasket. We replaced it and PROPERLY refilled the system and now all is good again.. just like it was before he messed with it!
Big Jim